1. Field of the Invention
The present invention relates to a cam target wheel for a vehicle, and more particularly, to a cam target wheel which can recognize vibration of a camshaft to improve the operability of the camshaft.
2. Description of Related Art
In general, engines employing continuously variable valve timing (CVVT) are provided with a cam target wheel for recognizing a cam phase.
A cam target wheel 101 for a vehicle in the related art includes, as shown in FIG. 1, a camshaft 110, and a lobe 120 protruding at a desired angle (θ′) from an outer circumferential surface of the camshaft 110. In this instance, the angle (θ′) of the lobe 120 is 180 degrees.
The conventional cam target wheel 101 including the semicircular lobe 120 calculates a phase with a square wave of 180° interval (360° for a crank). A torque variation of each cylinder due to explosion and a torque variation of the camshaft 110 occur for every cylinder, and these torque variations cause cams to periodically vibrate in unit of a cylinder (180°).
In particular, in an application to which the CVVT controlled by a hydraulic pressure is applied, the vibration of the camshaft 110 occurs periodically at an interval of 180°. However, since the semicircular cam target wheel 101 in the related art recognizes the phase of the camshaft 110 at an equal interval of 360° on the basis of the crank, there is a problem in that it cannot recognize the cam vibration.
That is, as shown in FIG. 2, in CASE 1 and CASE 2 which are conducted under the same driving conditions, an ECU recognizes that the cam shaft 110 is equally controlled on the basis of the signal from the sensor of the cam target wheel. In fact, however, there is a problem in CASE 2 in that the cam is excessively vibrated, but the ECU does not recognize the cam vibration because of the property of the semicircular shape. In particular, in the case where the cam is excessively vibrated, there is a drawback in that since valve open/close timing is changed, an engine output is deteriorated.
In order to solve the above problems, the outer circumferential surface of the camshaft 110 is provided with a plurality of lobes 120 to improve the ability to recognize the cam vibration. However, if a plurality of lobes 120 are provided, a significant change such as logic development or factory line change is needed to raise a manufacturing cost.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.